The present invention relates to seats for rock drill inserts and, more particularly, to seats made largely of tin.
In many rock drills, hard metal inserts, usually made of cemented carbide, are installed in holes in rock drill bit bodies and retained in the holes substantially by an interference fit. U.S. Pat. No. 3,970,158, which is incorporated by reference, discloses an embodiment of such a rock drill with a cemented carbide insert.
In the past, a lead sphere was inserted in the hole prior to installation of the insert. The lead sphere would be compressed by the insert to deform and form a seat for the insert, and would substantially fill any void between the bottom of the insert and the bottom of the hole. In this way, impact would be effectively transmitted from the bit body to the face of the insert through the deformed lead seat. Also, the lead seat would tend to distribute stresses around the hole bottom geometry, reducing a potential of damage to the bit body.
The use of lead as the seat material is problematic. Environmental regulations can make it difficult to dispose of used rock drills or seats for such rock drills. It is desirable to provide an alternative to using lead seats for rock drill inserts.
In accordance with an aspect of the present invention, a rock drilling bit comprises at least one button having a button sidewall and button bottom, the button sidewall and the button bottom having a button sidewall geometry and a button bottom geometry, respectively. The rock drilling bit further comprises a bit body having at least one button-receiving hole having a hole sidewall and a hole bottom, the hole sidewall and the hole bottom having a hole sidewall geometry complementary to the button sidewall geometry and a hole bottom geometry, and a deformable seat compressed between the buttom bottom and the hole bottom so that the seat conforms to a hole bottom geometry and the button bottom geometry, the seat comprising tin.
In accordance with another aspect of the present invention, a seat for a rock drilling button of a rock drilling bit comprises at least about 50% tin and has a volume adapted to completely fill a void between a bottom of a hole in a rock bit body and a bottom of the button when the button is properly positioned relative to the hole and compresses the seat.
In accordance with yet another aspect of the present invention, a method of mounting a button in a button-receiving hole of a rock drilling bit comprises inserting a deformable seat comprising at least 50% tin in a bottom of the hole, and compressing the seat between a bottom of the button and the bottom of the hole so that the seat completely conforms to a hole bottom geometry and a button bottom geometry.